We have been testing for the presence of growth factors in the cerebral spinal fluid (CSF) of normal and chronic schizophrenic human subjects. The test system uses neurite growth in cells from a neuroblastoma cell line (Neuro 2-A) to assay the presence of growth factors. Indirect growth factors that cause cells to secrete a diffusible growth substance have been demonstrated. Growth factors of unknown composition in CSF have also been demonstrated. However, they are found in normal and schizophrenic subjects with equal probability. Hydra peptide, and somatostatin cause neurite growth but nerve growth factor does not, in this system.